Despite extensive clinical and experimental investigation, the significance of observed areas of regional left ventricular dysfunction in patients with ischemic heart disease remains uncertain. In general, the total area of dysfunctional myocardium appears to be larger than that of infarcted myocardium. The studies described in this proposal are designed to provide further insight into the mechanisms by which regional left ventricular dysfunction occurs outside of the infarcted zone. The investigation will focus on the relationship between myocardial perfusion and regional function in central ischemic, peripheral ischemic, non-ischemic but adjacent, and distant non-ischemic myocardium in a canine model of ischemic heart disease. Questions to be addressed include 1) the extent of a dysfunctional ischemic border zone at the lateral margins of an infarct, 2) the presence of adjacent, nonischemic dysfunctional myocardium, 3) the correlation between sonomicrometer and two-dimensional echocardiographic assessment of regional left ventricular function, 4) dysfunction at a distance due to critical stenosis of a separate coronary artery, and the feasibility of differentiating necrotic, ischemic, and non-ischemic but dysfunctional myocardium using non-invasive techniques. The long term goal is to help optimize the diagnostic and therapeutic approach to patients with ischemic heart disease by providing an understanding of the mechanisms underlying regional left ventricular dysfunction in this disease.